Well, First you need to have unlocked the Elf at Cave 4. Then, After doing like 6 or 9 Quests, The Elf or Wayne is going to give you a quest to kill the boss. The Red ring means no Trespassing or in other words, "You Aquire a Potion" to use and make the Seal Dissapier.
ok guys, please, if you find a solution to the problem, please say what the solution is in the forum, not just "solved it". I have the same problem here.
Dual-headed ogre appears in random dead ends. There's also a guaranteed spawn somewhere in the teens (I think D14). That one has a level cap last I checked, so if fighting one that's around your level is too hard (which is quite likely), then grind up to around level 31 or so and take on the D14 one, which IIRC is capped at level 28.
If you find a random one it comes either at your level or one above your level, I haven't played in ages so I don't remember specifics. Either way, be prepared for a serious fight if you want to go looking for him.
SPOILER ALERT
That ogre is actually a weaker version of Arcuz 1's final boss, so if you somehow managed to beat Arcuz 1, you'll have no problem with him.